I was vaguely aware of the Martin Mars, a very large seaplane built in the 1940s for the U.S. Navy…but had no idea that any of these airplanes were still flying in commercial service.
Turns out that two of these planes–the Hawaii Mars and the Philippine Mars–are in regular use as water bombers for forest-fire fighting. Tailspin Tom has a great set of photographs.
Via Neptunus Lex, who notes that the Mars is less a flying boat than a flying ship.